The present invention relates to an information device having a security facility that provides the protection of data against unauthorized access by others and a method therefor, and more specifically to a portable information device that permits communications of electronic mail with no mail server involved and a method for providing the security of data.
In recent years, electronic mail by personal computers and word processors has spread rapidly to companies and individuals. In order for a company or an individual to employ electronic mail, it is required to install a host computer adapted for electronic mail in the company or join a commercial electronic mail service (personal computer communications service such as NIFTY Serve, or the like).
In the conventional electronic mail systems, mail (character string data) to be interchanged between information devices is stored in the bulk storage of an in-company electronic mail computer, called a mail server, or a commercial electronic mail service computer. Both the sender and the receiver make access to (call) the mail server mainly via telephone lines.
FIG. 1 shows a conventional electronic mail system. In the conventional system, information devices, such as personal digital assistants (PDAs), interchange mail via a mail server 2.
As an example, to send mail data from the information device 1a to the information device 1b, the information device 1a first makes access to the mail server 2 and then sends the mail data addressed to the information device 1b to the mail server 2. The information device 1b likewise makes access to the mail server and receives from the mail server the mail data addressed to it.
As described above, a mail server (computer) adapted to store and interchange mail data is dispensable for the conventional electronic mail system. That is, mail interchange between information devices cannot be achieved without making access to the mail server. Thus, it cannot be said that the conventional electronic mail system can be employed easily by anyone. For this reason, an implementation of a simple electronic mail system has been desired which, unlike the conventional electronic mail system, allows mail interchange among information devices with no mail server involved.
FIG. 2 shows an arrangement of such a simple electronic mail system. Information devices 10a, 10b and 10c each have a digital telephone facility built in. Each of the information devices is equipped with a facility for directly sending or receiving electronic mail to or from another information device. In this case, information devices can be used which have a built-in wireless telephone facility such as the personal handyphone system (PHS) which is a digital simplified telephone system adopted in Japan. With such an arrangement, electronic mail can be interchanged among the information devices 10a, 10b and 10c freely with no mail server involved.
If the simplified electronic mail system as shown in FIG. 2 is used in place of the conventional electronic mail system shown in FIG. 1, then mail data, which, in the conventional system, are managed by the mail server, will be managed by individual information devices. In this case, there will arise the following problems.
In the simplified electronic mail system, mail data are held on individual information devices. In case where the owner of an information device should leave it somewhere or he or she should have it stolen, there arises the possibility that another person may use it to know mail data. In this case, even if the owner is aware that the information device has been missing, he or she cannot take any countermeasures against it.
To solve the problem of data leakage to others, a method for security will be conceived which sets information devices to demand of each user the entry of a password each time he or she activates his or her information device to thereby allow data to be made open only to authorized users. With this method, however, users who have to activate and stop their information device over and over again a day will feel troublesome for an operation of entering a password each time they activate it. For this reason, it cannot be said that it is preferable to use such a method.